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NIAID-funded Researchers Find H1N1 Influenza Was Transmitted to Humans Several Months Before Recognition of the Outbreak (2009)

A team of researchers at Hong Kong University conducted an evolutionary analysis on the currently circulating 2009 novel H1N1 influenza virus to determine its origins and early developments. Led by Gavin Smith, M.D., and supported by the NIAID Centers of Excellence for Influenza Research and Surveillance (CEIRS), researchers found that the virus was derived from several viruses circulating in swine, and that the initial transmission to humans occurred several months before recognition of the outbreak.

A phylogenetic estimate of the gaps in genetic surveillance suggested a long period of unsampled ancestry before the outbreak, implying that the reassortment of swine lineages may have occurred years before the disease emerged in humans. These findings highlight the need for systematic surveillance of influenza in swine, and provide evidence that the mixing of new genetic elements in swine can result in the emergence of viruses with pandemic potential in humans.


GJ Smith et al. Origins and evolutionary genomics of the 2009 swine-origin H1N1 influenza A epidemic. Nature. 459(7250):1122-5 DOI: 10.1038/nature08182 (2009).

Last Updated March 06, 2013

Last Reviewed March 06, 2013